I own Pixel C and I own the Anker dongle which has Ethernet and USB sockets.
What I do is connect the dongle and the drive, copy off the file like a movie, I get good transfer times so it's only needed connected a few minutes. Then unplug dongle and plug in a Powercore in my case it depends on the flight length either the 10000 or the dual 2A 2.4A output 26800.
My Pixel C is 64GB, and HAD video is about 1GB/hour so easily able to store many hours of videos on internal storage.
I then either carry a 12ft mains extension cord and the Powerport4, or I carry the Powerport5 USBC. The Pixel C own charger doesn't feed more than 2.6A and the Powerport5 USBC gives out 2.6A, the Powerport4 gives out 2.2A so about 30% different recharge.